1. Field of the Invention
The present invention relates to a hydraulic pressure hose, and more particularly relates to a hydraulic brake hose for a vehicle.
2. Description of Related Art
In general, a hydraulic brake hose for a vehicle is constructed an inner rubber layer, a first braided fiber reinforced layer formed in the outer periphery of the inner rubber layer, an intermediate rubber layer formed in the outer periphery of the first braided fiber reinforced layer, a second braided fiber reinforced layer formed in the outer periphery of the intermediate rubber layer and an outer rubber layer formed in the outer periphery of the second braided fiber reinforced layer.
Vinylon fiber used for the hydraulic brake hose for a vehicle generally has 1200 deniers. As for a braiding machine for forming such a reinforced layer using such fiber, a braiding machine of 24 carrier type is commonly used. A braiding machine of 20 carrier type is sometime used.
A conventional first braided fiber reinforced layer employs braided fiber of 1200 deniers, 2-fiber yarn, 20 to 24 beatings.
The conventional brake hose described above has a disadvantage in that the braided fiber is easily lessened because of too much fiber. When the hose suffers repeating pressurizing, bending and twisting, the fatigue characteristic of the hose is often degraded by friction between the braided fibers. In addition to this, it is difficult to attain a static angle indicating the minimum value of expansion and contraction. Further, the diameter of the first braided fiber reinforced layer dominating the amount of hose expansion becomes large. Even when a high elastic fiber, for example, vinylon fiber is used for the braided fiber reinforced layer, the amount of hose expansion becomes large in the pressure range of actual use (0 to 50 kgf/cm2). As the result, there is a disadvantage in that these affect a bad influence on feeling of braking.
In a conventional technology disclosed in Japanese Patent Application Laid-Open No.5-248571, lower expansion and improved fatigue characteristic are attained by adjusting tensile strength of fiber. However, it is required to develop a hydraulic pressure hose using another method which can decrease the expansion rate and at the same time can improve the fatigue characteristic.
The present invention is developed to solve the above problems. An object of the present invention is to decrease the amount of expansion of a hydraulic pressure hose under pressure of 0 to 30 kgf/cm2 and to improve the fatigue characteristic against repeating pressurization, bending and twisting.
The present invention can substantially decrease the amount of expansion of a hydraulic pressure hose and improve the fatigue characteristic by properly selecting the diameter of fibers composing the hose and the outer diameter of each layer constructing the hose.
That is, the hydraulic pressure hose comprising an inner rubber layer, a first braided fiber reinforced layer formed in the outer periphery of the inner rubber layer, an intermediate rubber layer formed in the outer periphery of the first braided fiber reinforced layer, a second braided fiber reinforced layer formed in the outer periphery of the intermediate rubber layer and an outer rubber layer formed in the outer periphery of the second braided fiber reinforced layer, wherein the first braided fiber reinforced layer is formed of fibers having 950 deniers to 1050 deniers, the thickness of the first braided fiber reinforced layer being 0.30 mm to 0.50 mm.